# US 12,118,433 B2 · Space-saving coupler arm arrangement for superconducting qubits

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- Number: US 12,118,433 B2
- Document ID: US12118433B2
- Status: Granted
- Kind: B2
- Application number: 17/552,018
- Filed: 2021-12-15
- Published: 2023-06-15
- Granted: 2024-10-15
- Earliest claimed: 2021-12-15
- Assignees: International Business Machines Corporation
- Applicants: International Business Machines Corporation
- Inventors: Srikanth Srinivasan; George Andrew Keefe; David C. Mckay; Xuan Wei; Abhinav Kandala
- Web page: https://patentgrep.com/patent/US12118433B2

## CPC

- G06N 10/40: Physical realisations or architectures of quantum processors or components for manipulating qubits, e.g. qubit coupling or qubit control
- H10N 60/805: {for Josephson-effect devices}
- G06N: COMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR

## Abstract

Systems and techniques that facilitate space-saving coupler arm arrangement for superconducting qubits are provided. In various embodiments, a device can comprise a superconducting qubit. In various aspects, the superconducting qubit can be capacitively coupled to two or more coupler arms. In various instances, a parasitic capacitance between the two or more coupler arms can be within an order of magnitude of a capacitance between the superconducting qubit and at least one of the two or more coupler arms. In various cases, the parasitic capacitance can arise due to a physical proximity between the two or more coupler arms.

## Claims

### Claim 1

A device, comprising:
a first superconducting qubit capacitively coupled to a group of coupler arms, wherein a first pair of coupler arms of the group of couplers that are capacitively coupled to a second superconducting qubit are separated by a first defined distance selected to cause a first defined parasitic capacitance between a first coupler arm and a second coupler arm of the first pair of coupler arms that is within a first defined order of magnitude of a first defined capacitance between the first superconducting qubit and a first coupler arm of the first pair of coupler arms, wherein a second defined capacitance between the first superconducting qubit and a second coupler arm of the first pair of coupler arms is greater than the first defined capacitance, and wherein the first defined capacitance is selected to cause the first superconducting qubit to exhibit a defined quantum electrical behavior in response to presence of the first defined parasitic capacitance.

### Claim 2 (depends on 1)

The device of claim 1, wherein the defined parasitic capacitance is greater than 10% of the first defined capacitance.

### Claim 3 (depends on 1)

The device of claim 1, wherein the parasitic capacitance arises within a qubit pocket of the superconducting qubit, wherein the qubit pocket is located within a ground plane of the device.

### Claim 4 (depends on 1)

The device of claim 1, wherein the superconducting qubit is a transmon, and wherein the first defined capacitance exists between a planar capacitor pad of the transmon and the first coupler arm.

### Claim 5 (depends on 1)

The device of claim 1, wherein the group of coupler arms further comprises a second pair of coupler arms capacitively coupled to a third superconducting qubit and are separated by a second defined distance, wherein a third defined distance between the first pair of coupler arms and the second pair of couple arms is greater than the first defined distance and the second defined distance.

### Claim 6 (depends on 1)

The device of claim 1, further comprising a multi-order filter that comprises the group of coupler arms, a direct capacitive coupler, and a λ/4 resonator coupler.

### Claim 7 (depends on 1)

The device of claim 1, wherein the parasitic capacitance is between 10% of the first defined capacitance and 25% of the first defined capacitance, inclusively.

### Claim 8 (depends on 5)

The device of claim 5, wherein the second defined distance is selected to cause a second defined parasitic capacitance between a third coupler arm and a fourth coupler arm of the second pair of coupler arms that is within a second defined order of magnitude of a third defined capacitance between the third superconducting qubit and the third coupler arm, wherein a fourth defined capacitance between the first superconducting qubit and the fourth coupler arm is greater than the third defined capacitance, wherein the third defined capacitance is selected to cause the first superconducting qubit to exhibit the defined quantum electrical behavior in response to presence of the second defined parasitic capacitance capacitance is tuned to electrically compensate for the parasitic capacitance.

### Claim 9

A system, comprising:
a superconducting qubit capacitively coupled to a group of coupler arms;
wherein a first pair of coupler arms of the group of couplers are separated by a first defined distance selected to cause a first defined parasitic capacitance between a first coupler arm and a second coupler arm of the first pair of coupler arms that is within a first defined order of magnitude of a first defined capacitance between the superconducting qubit and at least one of the first pair of coupler arms, and wherein the first defined capacitance is selected to cause the first superconducting qubit to exhibit a defined quantum electrical behavior in response to presence of the first defined parasitic capacitance; and
wherein a second pair of coupler arms of the group of couplers are separated by a second defined distance selected to cause a second defined parasitic capacitance between a first coupler arm and a second coupler arm of the second pair of coupler arms that is within a second defined order of magnitude of a second defined capacitance between the superconducting qubit and at least one of the second pair of coupler arms, and wherein the second defined capacitance is selected to cause the first superconducting qubit to exhibit the defined quantum electrical behavior in response to presence of the second defined parasitic capacitance.

### Claim 10 (depends on 9)

The system of claim 9, wherein the first pair of coupler arms and the second pair of coupler arms are separated by a third defined distance that is greater than the first defined distance and the second defined distance.

### Claim 11 (depends on 9)

The system of claim 9, wherein the first defined parasitic capacitance and the second defined parasitic capacitance arise qubit pocket of the superconducting qubit, wherein the qubit pocket is located within a ground plane of a substrate of the system.

### Claim 12 (depends on 9)

The system of claim 9, wherein the superconducting qubit is a transmon, wherein the first defined capacitance exists between a planar capacitor pad of the transmon and the at least one of the first pair of coupler arms, and wherein the second defined capacitance exists between the planar capacitor pad of the transmon and the at least one of the second pair of coupler arms.

### Claim 13 (depends on 9)

The system of claim 9, wherein the first pair of coupler arms belong to a first multi-order filter that couples the superconducting qubit to a first other superconducting qubit, and wherein the second pair of coupler arms belong to a second multi-order filter that couples the superconducting qubit to a second other superconducting qubit.

### Claim 14 (depends on 13)

The system of claim 13, wherein at least one of the first multi-order filter and the second multi-order filter comprises a direct capacitive coupler and a λ/4 resonator coupler.

### Claim 15 (depends on 9)

The system of claim 9, wherein the first defined parasitic capacitance is between 10% of the first defined capacitance and 25% of the first defined capacitance, inclusively, and wherein the second defined parasitic capacitance is between 10% of the second defined capacitance and 25% of the second defined capacitance, inclusively.

### Claim 16

An apparatus, comprising:
a transmon qubit comprising a Josephson junction shunted by a planar capacitor; and
a group of coupler arms that are capacitively coupled to a pad of the planar capacitor, wherein a first pair of coupler arms of the group of coupler arms are separated by a first defined distance selected to cause a first defined cross-capacitance between a first coupler arm and a second coupler arm of the first pair of coupler arms that is within a first defined order of magnitude of a first defined capacitance between the pad and at least one of the first coupler arm or second coupler arm, and wherein the first defined capacitance is selected to cause the transmon qubit to exhibit a defined quantum electrical behavior in response to presence of the first defined cross-capacitance capacitance.

### Claim 17 (depends on 16)

The apparatus of claim 16, wherein the group of coupler arms belong to a multi-order filter that couples the transmon qubit to another transmon qubit.

### Claim 18 (depends on 16)

The apparatus of claim 16, wherein the first defined cross-capacitance is 20% of the first defined capacitance.

### Claim 19 (depends on 16)

The apparatus of claim 16, wherein a second pair of coupler arms of the group of coupler arms are separated by a second defined distance selected to cause a second defined cross-capacitance between a first coupler arm and a second coupler arm of the second pair of coupler arms that is within a second defined order of magnitude of a second defined capacitance between the pad and at least one of the first coupler arm or second coupler arm of the second pair of coupler arms, and wherein the second defined capacitance is selected to cause the transmon qubit to exhibit the defined quantum electrical behavior in response to presence of the second defined cross-capacitance capacitance.

### Claim 20 (depends on 16)

The apparatus of claim 16, wherein the first pair of coupler arms and the second pair of coupler arms are separated by a third defined distance that is greater than the first defined distance and the second defined distance.